Effective Disinfectants for Coccidioides immitis and C. posadasii

Modeling Chronic Coccidioidomycosis in Mice

Coccidioidomycosis, caused by the dimorphic pathogens Coccidioides posadasii and C. immitis, is a fungal disease endemic to the southwestern United States, Mexico, and some regions of Central and South America. The mouse is the primary model for studying pathology and immunology of disease. Mice in general are extremely susceptible to Coccidioides spp., which creates challenges in studying the adaptive immune responses that are required for host control of coccidioidomycosis. Here, we describe how to infect mice to model asymptomatic infection with controlled, chronic granulomas and a slowly progressive but ultimately fatal infection that has kinetics more similar to the human disease.

Efficacy of Disinfectants Against Tropical Race 4 Causing Fusarium Wilt in Cavendish Bananas

Fusarium wilt of banana (FWB), caused by a suite of Fusarium fungi, is among the most devastating plant diseases. The iconic FWB epidemic in the previous century lasted decades and was caused by so-called Race 1 strains that wiped out the dominant 'Gros Michel' banana plantations across Central America. Eventually, it was stopped because the Race 1-resistant 'Cavendish' banana variety replaced 'Gros Michel', which dominates global production (>50%) and trade (>95%). However, presently, the so-called Tropical Race 4 (TR4) threatens plantations of 'Cavendish' and many other banana varieties around the globe. Prevention is the first line of defense against the spread of TR4. Therefore, many disinfection units are installed to prevent the entry of TR4 in banana plantations. These foot and tire baths are filled with disinfectants, but limited knowledge is available on their efficacy. In this project, we evaluated 13 disinfectants commonly used in the Philippines. Our results show that the efficacy of these products depends on the type of fungal spores, the exposure time, and the replenishment frequency of the disinfection units. The resting spores of TR4 were resistant to all but one - unfortunately corrosive - disinfectant. Furthermore, we show that the actual contact time with disinfectants was far below the thresholds determined in laboratory experiments. Finally, muddy disinfection units reduced the efficacy of disinfectants. Taken together, we conclude that practices are inadequate to prevent the dissemination of TR4.

Proper Care and Feeding of Coccidioides: A Laboratorian's Guide to Cultivating the Dimorphic Stages of C. immitis and C. posadasii

Coccidioidomycosis ("Valley fever") is caused by Coccidioides immitis and C. posadasii. These fungi are thermally dimorphic, cycling between mycelia and arthroconidia in the environment and converting into spherules and endospores within a host. Coccidioides can cause a broad spectrum of disease that can be difficult to treat. There has been a steady increase in disease, with an estimated 350,000 new infections per year in the United States. With the increase in disease and difficulty in treatment, there is an unmet need to increase research in basic biology and identify new treatments, diagnostics, and vaccine candidates. Here, we describe protocols required in any Coccidioides laboratory, such as growing, harvesting, and storing the different stages of this dimorphic fungal pathogen. © 2020 Wiley Periodicals LLC. Basic Protocol 1: Growth and harvest of liquid mycelia cultures for extractions Alternate Protocol 1: Large-volume growth and harvest of liquid mycelia cultures Basic Protocol 2: Mycelial growth on solid medium Alternate Protocol 2: Maintaining mycelial growth on solid medium Basic Protocol 3: Harvesting and quantification of arthroconidia Alternate Protocol 3: Long-term storage of arthroconidia Basic Protocol 4: Parasitic spherule growth and harvest Alternate Protocol 4: Obtaining endospores from spherules Basic Protocol 5: Intranasal infection of murine models.

Characterizing in vitro spherule morphogenesis of multiple strains of both species of Coccidioides

The disease San Joaquin Valley Fever (coccidioidomycosis) is caused by the inhalation of Coccidioides arthroconidia. In vivo, arthroconidia transform into pathogenic structures termed spherules. Exposure to the host milieu triggers spherule development; however, the molecular mechanisms responsible for the morphological shift are not well characterized. This study compared the morphogenesis of five strains of both species of Coccidioides in two media types to improve the in vitro model of dimorphism that can be easily reproduced, and is amenable to tissue culture. We also sought to establish a modern record of the morphological switch among commonly used lab strains through a detailed account of growth under various conditions. Spherules from five strains were grown in standard (Converse) and experimental media (RPMI-sph). Strain behavior was quantified by median spherule size and spherule concentration, beginning 3 days after inoculation and followed for 10 days of growth. There were significant differences observed among Coccidioides immitis and C. posadasii strains, as well as differences between the in vitro systems.

Laboratory exposure to Coccidioides: lessons learnt in a non-endemic country

Coccidioides is a primary pathogenic fungus, which infects humans through highly infectious arthroconidia, causing substantial morbidity including life-threatening disseminated infections. Due to the low infectious dose, laboratory personnel might become infected during diagnostic procedures. Accordingly, coccidioidomycosis is reported as the most frequent laboratory-acquired systemic mycosis worldwide. This risk is aggravated in non-endemic countries, where the diagnosis may not be suspected. We report on an inadvertent exposure of 44 persons to Coccidioides posadasii in a clinical microbiology laboratory in Chile, the measures of containment after rapid diagnosis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and the lessons learnt in a non-endemic setting.

Evaluation of Virex® II 256 and Virex® Tb as Disinfectants of the Dimorphic Fungi Coccidioides immitis and Coccidioides posadasii

To date, limited published data exists regarding the efficacy of commonly used disinfectants in inactivating the Risk Group 3 dimorphic fungal pathogens, Coccidioides immitis and Coccidioides posadasii. Newer generation quaternary ammonium compounds, like Virex® II 256 and Virex® Tb, have not been previously evaluated. Herein, these disinfectants are evaluated against 10% bleach and 70% ethanol, for their ability to inactivate 5×10⁷ arthroconidial spores of C. immitis RS or C. posadasii strain Silveira within 2, 5, 10 or 20 minutes contact time in aqueous solution. Evidence is provided that both Virex® II 256 and Virex® Tb are highly effective alternatives to 10% bleach or 70% ethanol for the disinfection of 5×10⁷ arthroconidia of Coccidioides spp. within 2 minutes of contact time. 70% ethanol was seen as less effective in killing C.immitis RS arthroconidia and both 70% ethanol and 10% bleach were seen as less effective than the other disinfectants in killing C. posadasii strain Silveira, as longer contact times were required to completely inactivate the same number of arthroconidia.